Ground flares

ABSTRACT

A ground flare with a combustion zone defined by a floor and walls constructed from earthen banks, stone, rock, bricks or the like. Tubes leading through the walls into the interior of the flare to convey primary combustion air to the combustion zone. A manifold disposed beneath the floor of the flare leads to a series of nozzles projecting upwardly from the flare which serve to discharge a waste gas into the combustion zone. Pilot burners are provided to ignite the waste gas. Some of the nozzles are each surmounted by an air moving device which is fed with steam. The steam flows over a Coanda annulus and serves to induce ambient air into the waste gas discharged by the nozzle.

nited States Patent [191 Proctor et al.

July 9, 1974 Primary ExaminerEdward G. Favors Attorney, Agent, orFirm-Chittick, Thompson & Pfund [5 7] ABSTRACT A ground flare with acombustion zone defined by a floor and walls constructed from earthenbanks, stone, rock, bricks or the like. Tubes leading through the wallsinto the interior of the flare to convey primary combustion air to thecombustion zone. A manifold disposed beneath the floor of the flareleads to a series of nozzles projecting upwardly from the flare whichserve to discharge a waste gas into the combustion zone. Pilot burnersare provided to ignite the waste gas. Some of the nozzles are eachsurmounted by an air moving device which is fed with steam. The steamflows over a Coanda annulus and serves to induce ambient air into thewaste gas discharged by the nozzle.

16 Claims, 7 Drawing Figures GROUND FLARES [75] Inventors: Albert EdwardProctor, New

Denham, England; Giovanni Castorani, Milan, Italy [73] Assignee: A. E.Proctor & Montecatini Edison S.p.A., Milan, Italy [22] Filed: Apr. 23,1973 [21] Appl. No.: 353,686

[52] US. Cl 431/202, 23/277 C, 431/5 [51] int. Cl. F23d 13/20 [58] Fieldof Search 431/202, 5; 23/277 C [56] References Cited UNlTED STATESPATENTS 2,802,521 8/1957 Campbell 431/202 3,554,651 1/1971 Proctor3,749,546 7/1973 Reed et al 431/5 PATENTEBJUL W I 3,822.983

sum 1 0F 5 PATENTEI] JUL 91574 SHEET3UF5 Q Fig.3

\ FQQQQQQ i 18 Fig.7

62 nmu PATENTEUJUL awn SHEET 4 0F 5 GROUND FLARFS BACKGROUND OF THEINVENTION The present invention relates to ground flares for disposingof waste or dump gas primarily in the petrochemical field.

Flares are widely used for disposing of waste gas and generally suchflares are classed as ground or elevated flares.

A general object of the invention is to provide an improved ground flarewith particular regard to achieving substantially smokeless combustion.

. SUMMARY OF THE INVENTION In its broadest aspect the invention providesa ground flare comprising means for defining a combustion zone, and aplurality of nozzles for discharging a combustible waste gas into saidzone, at least one of the nozzles being operably associated with an airmoving or inducing device which operates in the manner known as theCoanda effect.

The invention also provides a ground flare comprising means for defininga combustion zone, means for conveying air to said zone, a plurality ofnozzles for discharging a waste gas for combustion in said zone, airinducing devices which operate on the Coanda principle operablyassociated with at least some of the nozzles and means for feeding aninducing medium, preferably steam, to each of said devices to induce airto mix with the gas discharged from the nozzle associated therewith,whereby to effect substantially smokeless combustion.

Although steam is a preferred inducing medium any fluid generally havinga higher pressure than that of the waste gas can be used.

In a preferred arrangement each nozzle having an air inducing deviceassociated therewith discharges gas into the air inducing device and thedevice in turn discharges a mixture of gas, air and the inducing mediuminto the combustion zone. Combustion of the resultant mixture togetherwith waste gas discharged by others of the nozzles is effected by meansof pilot burners known per se. A ground flare made in accordance withthe foregoing is found to achieve substantially smokeless combustion,and this can be controlled by varying the pressure of the inducingmedium so as to cause more or less air to be introduced into thecombustion-zone.

The combustion zone may be substantially rectangular in plan view anddefined by walls fabricated from earth banks lined with a refractorymaterial. It is also possible for the zone to be defined by metallicwalls forms as a box again lined with a refractory material. In thislatter construction the walls may be fabricated on a modular basis withstandard units joined end-toend to form a zone of the desired size andcapacity.

In a ground flare made in accordance with the invention the nozzles maybe arranged in rows at ground level and fed with gas from an undergroundmanifold. Some of the nozzles perhaps every other one or two in a rowwould have an air inducing device assembled therewith while theremaining nozzles serve simply to discharge gas directly into thecombustion zone with the existing devices inducing air into the gasdischarged from those nozzles also. In a further modification some ofthe simpler nozzles may be provided with sealing to be disposed of risesabove a pre-determined amount.

In apreferred form the, or each, air inducing device has a body with acentral bore of aerofoil section communicating with an air inlet at oneend of the body, a chamber with an outlet adapted to receive inducingmedium, and an internal Coanda annulus over which the inducing mediumflows to induce air flow through the bore in combination with theinducing medium. 7 The device may then be supported on its associatednozzle and spaced apart therefrom to permit waste gas discharged fromthe nozzle to enter the inlet in addition to the air so that the devicedischarges a mixture of the waste gas, air and the inducing medium intothe combustion zone.

In one ground flare made in accordance with the invention the maximumquantity of gas that can be handled is typically 90 tons per hour butthere is no strict limitation on this figure.

The invention may be understood more readily, and various other featuresof the invention may become more apparent, from consideration of thefollowing description.

BRIEF DESCRIPTION OF DRAWINGS An embodiment of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings, wherein:

FIG. 1 isa part-sectional end view of a ground flare made in accordancewith the invention;

FIG. 2 is a plan view of part of the ground flare;

FIG. 3 is a side view of part of the ground flare;

FIG. 4 is a perspective view showing part of the flare in conjunctionwith the associated pipework and pressure vessel;

FIG. 5 is an enlarged sectional end view of the gas manifold of theflare showing simple forms of outlet nozzles; 3

FIG. 6 is a diagrammatic representation of an assembly of a gas nozzleand an air moving device; and

FIG. 7 is a longitudinal sectional view of the air moving deviceshown'in FIG. 6.

DESCRIPTION OF PREFERRED EMBODIMENT temally with a course of stone,rock, brick or the like. The internal lining, denoted 14, can be arefractory material and is inclined upwardly and outwardly from thefloor 16 of the zone 10 as can be best seen in FIG. 1.

At the base of each side wall 11 there is provided a series of paralleltubes 15 set in concrete and arranged transversely to the longitudinalaxis of the floor 16. The tubes 15, which are open at both ends, serveto convey primary combustion air into the zone 10.

A manifold 17, in the form of a pipe closed at its ends, is disposedbelow ground level and at the longitudinal centre of the floor 16. Themanifold 17 communicates with a supply pipe 24 extending transverselythereto and exteriorly of one of the walls 11. The pipe 24 serves toconvey a combustible waste gas to the manifold 17 for disposal in thezone 10. The upper peripheral part of the manifold 17 is provided withtwo rows of inclined nozzles 20 which project above the floor 16. Eachrow of nozzles 20 is disposed along a line disposed parallel to andlaterally offset from the longitudinal axis of the floor 16. The nozzles20 are generally directed towards the inner surfaces 14 of the walls 11.The nozzles 20 communicate with the interior of the manifold 17.

A drain cock 26 also communicates with the manifold 17 via an inclineddrain pipe 50 at each end of the manifold 17. These drain cocks 26 serveto allow liquid condensate to be removed from the manifold 17.

Laid along the outside of one of the walls 11 there are groups ofconduits 21. The conduits 21 include gas and air conduits leading topilot burners 22, via some of the tubes 15, and a steam conduit leadingto a steam manifold 23 by means of one or more sub-conduits laid belowthe ground level. The manifold 23 is, in this construction, formed fromtwo interconnected tubes disposed beneath the floor 16 at the bases ofthe side walls 1 I.

As shown in FIG. 4, the pipe 24 feeding the manifold 17 is taken aboveground level to a pressure vessel 30. The vessel 30 is part filled withwater and forms a water seal generally known per se. The vessel 30 is inturn fed from a pipe 31 leading to a main waste gas supply pipe.

The nozzles 20 take two basic forms one of which is shown in FIG. 5. Inthis form the nozzle 20 is a simple open ended tube set in an aperturein the manifold 17 and affixed thereto. A flame retention head 66 isprovided at the outer end of the nozzle 20.

In the second form the nozzle 20 shown in FIG. 5, but without the head66 is supplemented by an air moving or inducing device. The resultantassembly is depicted in FIGS. 6 and 7. As shown in FIG. 6, the nozzle 20is surmounted by a bracket 27, composed of rods 67, attached to theupper end of the nozzle 20. The bracket 27 is used to support an airmoving device 28.

This device 28, which is shown in more detail in FIG. 7, has an inlet 80which is fed with steam from the steam manifold 23. The flow path of thesteam induces air, depicted by the arrow A, and supplied from the pipesto enter the device 28 and mix with the waste gas, depicted by the arrowG. discharged from the nozzle therebeneath. The steam actually mixeswith the air and gas so that the device 28 discharges from its upper enda mixture of gas, air and steam, depicted by the arrow K, which mixtureis subsequently combusted in the zone 10 and substantially in asmoke-free manner. Referring now to FIG. 7, the device 28 has a bodywith a central bore 62 of aerofoil section communicating with an airinlet 63 at one end of the body. The device has an internal Coanda"annulus, denoted 60, over which steam introduced into a chamber 61 viathe inlet 80 flows to induce air to flow into the inlet 63 and throughthe bore 62 in combination with the steam. The inducement of the air toflow as a stream through the device 28 by the passage of the steam inthis manner is known as the Coanda effect. The device 28 thus operatesin the manner known as the Coanda effect to induce air to flow throughthe device by utilizing steam as an inducing medium.

Some of the nozzles 20 may be provided with the device 28 and some ofthe nozzles 20 would take the form illustrated in FIG. 5 since onedevice 28 may be sufficient to supply air and steam for several nozzles.A further refinement would be to provide each of a further group of thesingle nozzles 20 (FIG. 5) with a weighted sealing cap or some othersealing means. This sealing means would normally close the nozzle 20associated therewith and would only open when the pressure of the gas inthe manifold rose above a pre-set level. In this way the group ofnozzles 20 having these caps can be used as auxiliary gas dischargenozzles.

The actual numbers and positionings of the nozzles 20 which take theforms represented in FIGS. 5 to 7 and the modified form as discussedabove depends upon a variety of factors'and would be determined bydesign and particular requirements. The operation of the ground flare isas follows:

In a typical petro-chemical installation the waste or dump gas supplyarrangement would feed the ground flare as well as one or more elevatedflares sometimes called flare stacks. These elevated flares wouldnormally operate where higher quantities of waste gas have to bedisposed of. The ground flare would normally operate with lowerquantities of waste gas say typically 5 10 tons per hour. The vessel 30effectively forms a one-way valve which only permits waste gas to flowin the direction of the manifold 17. Where the latter is fed with gasthis gas is dicharged by at least some of the nozzles 20 incorporatingthe devices 28 (FIGS. 6 and 7) into the zone 10 and is supplemented bygas discharged from the simple nozzles 20 (FIG. 1). The resultantmixture of steam, gas and air discharged into the zone 10 is combustedby operating one or more of the pilot burners 22. The subsequentcombustion is substantially smoke free even with heavier waste gases andby controlling the pressure of the steam, (say from 10 to I00 lbs. persquare inch) the amount of air entering the zone 10 for supportingcombustion and hence the combustion process itself can be controlled.However the effect of varying the steam pressure also enables thesmokeless fonn of combustion to be controlled for various types andmixtures of waste gases.

We claim 1. In a ground flare comprising a combustion zone, means forconveying air to said combustion zone and means for conveying a wastecombustible gas to said combustion zone; the improvement comprising aplurality of nozzles for discharging the combustible waste gas into theconbustion zone with at least one of the nozzles being operablyassociated with an air inducing device which operates in the mannerknown as the Coanda effect.

2. A ground flare according to claim 1, wherein some of the plurality ofnozzles are each associated with an air inducing device] 3. A groundflare according to claim 1, and further comprising means for feeding aninducing medium to the air inducing device.

4. A ground flare according to claim 1, and further comprising means forfeeding steam to the air inducing device, the steam serving to induceair to mix with the gas so that a mixture of gas, air and steam isdischarged from the associated nozzle into the combustion zone.

5. A ground flare according to claim 3, wherein there is provided meansfor varying the pressure of the inducing medium to control thecombustion process.

6.- A ground flare according to claim 4, wherein there is provided meansfor varying the pressure of the steam to control the combustion process.

7. A ground flare according to claim 1, and further comprising pilotburners for igniting the waste gas. 7

8. A ground flare according to claim 1, wherein the combustion zone isrectangular in plan view and is defined by walls lined internally with arefractory material, the nozzles projecting upwardly from the floor ofthe zone and communicating with a manifold laid below ground level.

9. A ground flare according to claim 8, wherein some of the walls havetubes extending therethrough, the tubes constituting means for conveyingair to the zone.

10. A ground flare according to claim 8, wherein the nozzles arearranged in rows extending longitudinally of the zones and each nozzleis inclined towards one of 12. A groud flare according to claim 8,wherein the manifold communicates with one or more drain pipes and draincocks permitting liquid to be drained from the manifold.

13. A ground flare according to claim 1, wherein some of the nozzleshave sealing means adapted to open when the quantity of waste gas to bedisposed of rises above a predetermined amount.

14. A ground flare according to claim 1, wherein the air inducing devicehas a body with a central bore of aerofoil section, communicating withan air inlet at one end of the body, a chamber with an outlet adapted toreceive inducing medium, and an internal Coanda annulus over which theinducing medium flows to induce air to flow through the bore incombination with the inducing medium.

15. A ground flare according to claim 14, wherein the airinducing'device is supported on its associated nozzle and spaced aparttherefrom to permit waste gas discharged from the nozzle to enter theinlet in addition to the air so that the device discharges a mixture ofthe waste gas, air and the inducing medium into the combustion zone.

16. A ground flare comprising means for defining a combustion zone,means for conveying air to said zone, a plurality of nozzles fordischarging a waste gas for combustion in said zone, air inducingdevices which operate on the Coanda principle operably associated withat least some of the nozzles and means for feeding an inducing medium,to each of said devices to induce air to mix with the gas dischargedfrom the nozzle associated therewith whereby to effect substantiallysmokeless combustion.

1. In a ground flare comprising a combustion zone, means for conveyingair to said combustion zone and means for conveying a waste combustiblegas to said combustion zone; the improvement comprising a plurality ofnozzles for discharging the combustible waste gas into the conbustionzone with at least one of the nozzles being operably associated with anair inducing device which operates in the manner known as the Coandaeffect.
 2. A ground flare according to claim 1, wherein some of theplurality of nozzles are each associated with an air inducing device. 3.A ground flare according to claim 1, and further comprising means forfeeding an inducing medium to the air inducing device.
 4. A ground flareaccording to claim 1, and further comprising means for feeding steam tothe air inducing device, the steam serving to induce air to mix with thegas so that a mixture of gas, air and steam is discharged from theassociated nozzle into the combustion zone.
 5. A ground flare accordingto claim 3, wherein there is provided means for varying the pressure ofthe inducing medium to control the combustion process.
 6. A ground flareaccording to claim 4, wherein there is provided means for varying thepressure of the steam to control the combustion process.
 7. A groundflare according to claim 1, and further comprising pilot burners forigniting the waste gas.
 8. A ground flare according to claim 1, whereinthe combustion zone is rectangular in plan view and is defined by wallslined internally with a refractory material, the nozzles projectingupwardly from the floor of the zone and communicating with a manifoldlaid below ground level.
 9. A ground flare according to claim 8, whereinsome of the walls have tubes extending therethrough, the tubesconstituting means for conveying air to the zone.
 10. A ground flareaccording to claim 8, wherein the nozzles are arranged in rows extendinglongitudinally of the zones and each nozzle is inclined towards one ofthe side walls.
 11. A ground flare according to claim 8, wherein themanifold communicates with a waste gas feed pipe taken above groundlevel exteriorly of the walls and leading to a pressure vesselincorporating a water seal.
 12. A groud flare according to claim 8,wherein the manifold communicates with one or more drain pipes and draincocks permitting liquid to be drained from the manifold.
 13. A groundflare according to claim 1, wherein some of the nozzles have sealingmeans adapted to open when the quantity of waste gas to be disposed ofrises above a predetermined amount.
 14. A ground flare according toclaim 1, wherein the air inducing device has a body with a central boreof aerofoil section, communicating with an air inlet at one end of thebody, a chamber with an outlet adapted to receive inducing medium, andan internal ''''Coanda'''' annulus over which the inducing medium flowsto induce air to flow through the bore in combination with the inducingmedium.
 15. A ground flare according to claim 14, wherein the airinducing device is supported on its associated nozzle and spaced aparttherefrom to permit waste gas discharged from the nozzle to enter theinlet in addition to the air so that the device discharges a mixture ofthe waste gas, air and the inducing medium into the combustion zone. 16.A ground flare comprising means for defining a combustion zone, meansfor conveying air to said zone, a plurality of nozzles for discharging awaste gas for combustion in said zone, air inducing devices whichoperate on the Coanda principle operably associated with at least someof the nozzles and means for feeding an inducing medium, to each of saiddevices to induce air to mix with the gas discharged from the nozzleassociated therewith whereby to effect substantially smokelesscombustion.